This application for a Mentored Clinical Scientist Development Award has the long-term objective of developing the applicant's ability to conduct independent research in developmental psychopathology, specifically, temperamental risk factors and their biological correlates in children at risk for anxiety disorders. Rachel Klein, Ph.D., primary sponsor, will oversee training of the applicant in methodology, assessment and data interpretation. Jack Gorman, M.D. will supervise biological studies, and physiology training. Training will be accomplished by means of: 1) supervision with experienced researchers, 2) internships in cardiac physiology, respiratory physiology, and brain function, 3) formal instruction in statistics, and 40 implementation of the research project. Course work will provide the necessary background in biostatistics and epidemiology to conduct data analyses. Training in data collection processing and analysis will be obtained through carrying out the Research Plan. The purpose of the research is to further understanding of the developmental psychopathology of anxiety disorders through the study of early temperament. The goal is to conduct an in-depth examination of behaviorally inhibited temperament and its biological correlates in at-risk children. Specific aims are to examine the relationship between behavioral inhibition and 1) parental anxiety disorders, and 2) physiological function exploring the influence of parental diagnosis on these relationships. These aims will be addressed through a top-down, high-risk study of 3-5 year old offspring of adults with lifetime panic disorder, social phobia, or major depression, and offspring of normals. Behavioral inhibition will be qualified through direct observational protocols blind to parent diagnosis. Biological procedures examine autonomic dysregulation of cardiac function and skin temperature, asymmetries of brain electrical activation and skin temperature. HPA Axis, and respiratory function. Measures of autonomic function include: 1) heart rate (HR), 2) heart rate variability (HRV) and spectral analysis of HRF, 3) acceleration of HR, 4) blood pressure, and 5) skin temperature. Techniques of quantitative EEG measure brain activational asymmetry. Salivary cortisol measures HPA Axis dysregulation. Measures of respiratory function include end-tidal carbon dioxide, respiratory rate, tidal volume, and minute ventilation. These have been implicated in behavioral inhibition and anxiety disorders. The study of risk factors has important implications for early identification and ultimately prevention.